carbon in cylinders/plugs.....problem

[Chevy II]

last night as I checked my oil pump part number I thought I would pull all the spark plugs to see is any looked damaged or worn. Now the engine has always run fine and still does. The plugs weren't covered but had alot of small carbon pieces on them and in the cylinders/piston tops. The carbon seemed to be soft and very moist. The engine had 65 hours when purchased and not sureif a fuel additive was used. I put in 16oz per 24 gals seafoam to clean and have about 1.5 full tanks through now. Is this just all the old crap being removed? I was going to run a 1oz/1gal of seafoam on the fourth tank and now I'm no sure what to do. Next tuesday it goes in for the oil pump and a racor filter. I will have the tech also look at that time. Is there a way to decarbonize the cylinders fast in the tank then have the plugs changed and maybe the O2 cleaned? Suggestions to fix or cause? (10/-4 225hp hpdi)

[BuzzB8]

I'd think it's the carbon being removed (hopefully in small pieces). Use a flashlight and look into the cylinders at the piston crowns...are they all clean? If so, just continue using at a rate you're comfortable with, maybe at a lower ratio for maintenance. If there's still some carbon then I'd use the ratio you've been using.